Electrical switch with a sealing member for use with an electrical device

ABSTRACT

An electrical switch unit for use in controlling operation of an electrical device, the electrical switch unit including: an electrical switch unit housing for housing at least a pair of electrical switching contacts of the electrical switch unit, said electrical switch unit housing including a first housing member and a second housing member that are configured for attachment together at peripheral regions of the first and second housing members so as to cooperatively form an enclosed space for housing the pair of electrical switching contacts therein; an actuator member operably-connected with at least one of the pair of electrical switching contacts, the actuator being configured for movement relative inwardly and outwardly of an opening in the electrical switch unit housing so as to arrange the pair of electrical switching contacts into at least one of a closed configuration wherein power is able to be supplied from a power source to motor or other electrically-operable element of the electrical device via the pair of electrical switching contacts, and, an opened configuration wherein power is not able to be supplied from the power source to the motor or other electrically-operable element of the electrical device via the pair of electrical switching contacts; and an sealing element including an elastically-resilient polymeric material, said sealing element being configured for location between the first and second housing members and extending about the peripheral regions of the attached first and second housing members so as to occlude passage and ingress of particulates and water into the electrical switch unit housing.

TECHNICAL FIELD

The present invention relates to the field of electrical switch units,and in particular relates to electrical switches for use in electricaldevices, such as hand-held power tools, personal care devices and homeelectrical appliances.

BACKGROUND OF THE INVENTION

Hand-held electrical devices such as power tools, personal care devicesand home electrical appliances may typically include electric switchunits which assist in controlling the supply of power to the motor orother electrically operable elements of the device.

It is of paramount importance that due to environmental factors, suchelectrical switches prevent ingress of foreign particulates such as dustand water. This is due to longevity of a switch, which typically may beused for numerous cycles when implemented in such devices andappliances. Also, and importantly, from an occupational health andsafety risk standpoint, it is important that ingress of foreign matterand water be prevented from entering a switch, as the ingress of suchmatter can cause short-circuiting as well as electric shock to anoperator. Further, such ingress may result in degradation andnon-operability of the electrical switch due to exposure of theelectrical switch components to foreign particulates such as dust andwater.

Depending upon the physical and environmental application, an electricalswitch is required to have a requisite level of particulate, dust andwater prevention to ingress rating. For example, hand-operable powertools are often exposed to harsh environments such as construction orwork sites, whereby there is inherently a high level of dust andparticulate matter, as well as often moisture and water. Further, anoperator of such devices may have wet hands or gloves with liquidthereon, such as uncured cement or wet paint, which needs to beprevented from entering the electrical switch. Also, a power tool whennot used may be laid down in a wet or moist environment or be exposed tothe splashing of water. In other applications such as personal caredevices, for example hairdryers, inherently there will exist airborneparticulate matter as well as water from the hair of an operator or wetsurfaces upon which a hairdryer or other device may be laid to rest.Accordingly, from longevity and safety standpoints, ingress into theswitch or switch assembly of particulates, dust and water must besuitably resisted or prevented.

Various approaches have been adopted to address the above-describedproblem. For instance, O-rings may be located adjacent to openings inthe electrical switch housing, for instance, at the opening where're thetrigger actuator enters the electrical switch housing to provide abarrier against ingress of dust and water. However, as O-rings have afixed shape and geometry they are suitable for sealing specific regionsof an electrical switch housing and are not suitable for sealing regionsof the electrical switch housing having non-flat or otherwise irregularshaped surface contours. Alternatively, resins may be used topermanently encapsulate or “potting” electrical and mechanicalcomponents of an electrical switch. However, this approach is alsoinflexible in that once the resin hardens around the electrical andmechanical components of the electrical switch, they cannot then bedisassembled, for instance if a faulty component is identified duringquality control testing of the electrical switch at the time ofmanufacture. In certain existing electrical switch units, two sectionsof an electrical switch housing may be bonded together using anultrasonic bonding technique in seeking to produce a water proof sealbetween the housing sections. However, it has been found that ultrasonicbonding tends to be imperfect, resulting in gaps along the join betweenthe two sections of the housing member rendering the electrical switchcomponents exposed to particulates and water that are able to passtherethrough. Furthermore, ultrasonic bonding may result in damage tothe components of the electrical switch unit and once bonded together,also does not allow for disassembly of the electrical switch housing ifrequired to replace a faulty component.

SUMMARY OF THE INVENTION

The present invention seeks to alleviate at least one of theabove-described problems.

The present invention may involve several broad forms. Embodiments ofthe present invention may include one or any combination of thedifferent broad forms herein described.

In a first broad form, the present invention provides an electricalswitch unit for use in controlling operation of an electrical device,the electrical switch unit including: an electrical switch unit housingfor housing at least a pair of electrical switching contacts of theelectrical switch unit, said electrical switch unit housing including afirst housing member and a second housing member that are configured forattachment together at peripheral regions of the first and secondhousing members so as to cooperatively form an enclosed space forhousing the pair of electrical switching contacts therein; an actuatormember operably-connected with at least one of the pair of electricalswitching contacts, the actuator being configured for movement relativeinwardly and outwardly of an opening in the electrical switch unithousing so as to arrange the pair of electrical switching contacts intoat least one of a closed configuration wherein power is able to besupplied from a power source to motor or other electrically-operableelement of the electrical device via the pair of electrical switchingcontacts, and, an opened configuration wherein power is not able to besupplied from the power source to the motor or otherelectrically-operable element of the electrical device via the pair ofelectrical switching contacts; and an sealing element including anelastically-resilient polymeric material, said sealing element beingconfigured for location between the first and second housing members andextending about the peripheral regions of the attached first and secondhousing members so as to occlude passage and ingress of particulates andwater into the electrical switch unit housing. Typically said sealingelement includes an sealing element.

Preferably, the sealing element may be configured to complement athree-dimensional shape contour of the peripheral region of the first orsecond housing member.

Preferably, the present invention may include at least one of a recessand a groove disposed along the peripheral region of at least one of thefirst and second housing members configured for seating the sealingelement therein.

Preferably, the sealing element may include an overmold.

Preferably, the sealing element may include at least one of a rubber, afoam, and a thermoplastic material.

Preferably, the sealing element may include a cross-sectional shapecontour including at least one peak and one trough region. Morepreferably, the cross-sectional shape contour may include a saw-toothcross-sectional shape contour.

In a further broad form, the present invention provides a method ofproducing an electrical switch unit for use in controlling operation ofan electrical device, the method including steps of: (i) providing anelectrical switch unit housing for housing at least a pair of electricalswitching contacts of the electrical switch unit, said electrical switchunit housing including a first housing member and a second housingmember that are configured for attachment together at peripheral regionsof the first and second housing members so as to cooperatively form anenclosed space for housing the pair of electrical switching contactstherein; (ii) providing an actuator member operably-connected with atleast one of the pair of electrical switching contacts, the actuatorbeing configured for movement relative inwardly and outwardly of anopening in the electrical switch unit housing so as to arrange the pairof electrical switching contacts into at least one of a closedconfiguration wherein power is able to be supplied from a power sourceto motor or other electrically-operable element of the electrical devicevia the pair of electrical switching contacts, and, an openedconfiguration wherein power is not able to be supplied from the powersource to the motor or other electrically-operable element of theelectrical device via the pair of electrical switching contacts; and(iii) providing a sealing element including an elastically-resilientpolymeric material, said sealing element being configured for locationbetween the first and second housing members and extending about theperipheral regions of the attached first and second housing members soas to occlude passage and ingress of particulates and water into theelectrical switch unit housing. Typically the sealing element mayinclude an sealing element.

Preferably, the present invention may include a step of forming thesealing element to complement a three-dimensional shape contour of theperipheral region of the first or second housing member.

Preferably, the present invention may include at step of forming atleast one of a recess and a groove disposed along the peripheral regionof at least one of the first and second housing members configured forseating the sealing element therein.

Preferably, the sealing element may include an overmold.

Preferably, the present invention may include a step of forming thesealing element from at least one of a rubber, a foam, and athermoplastic material.

Preferably, the present invention may include a step of forming thesealing element wherein a cross-sectional shape contour of the sealingelement includes at least one peak and one trough region. Morepreferably, the cross-sectional shape contour may include a saw-toothcross-sectional shape contour.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thefollowing detailed description of a preferred but non-limitingembodiments thereof, described in connection with the accompanyingdrawings, wherein:

FIG. 1A shows a top perspective view of an electrical switch unit inassembled form in accordance with one embodiment of the presentinvention;

FIG. 1B shows a perspective cross-sectional view of the electricalswitch unit of FIG. 1A in accordance with one embodiment of the presentinvention;

FIG. 2A shows a cross-sectional side-view of the assembled electricalswitch unit shown in FIG. 1A in accordance with one embodiment of thepresent invention;

FIG. 2B shows a magnified cross-sectional side-view of one aspect of theassembled electrical switch unit shown in FIG. 2A in accordance with oneembodiment of the present invention;

FIG. 2C shows a magnified cross-sectional side-view of another aspect ofthe assembled electrical switch unit shown in FIG. 2A in accordance withone embodiment of the present invention;

FIG. 3A shows a top perspective view of the electrical switch unit ofFIG. 1 with the top housing member removed to reveal anelastically-resilient overmold sealing member seated in a recessdisposed along the peripheral region of the lower housing member andextending about the peripheral region of the lower housing member;

FIG. 3B shows a top view of the electrical switch unit of FIG. 3A withthe top housing member removed to reveal an elastically-resilientovermold sealing member seated in a recess disposed along the peripheralregion of the lower housing member and extending about the peripheralregion of the lower housing member;

FIG. 4A shows a rendered drawing of a top perspective view of anelectrical switch unit with the top housing member removed to reveal anelastically-resilient overmold sealing member seated in a recessdisposed along the peripheral region of the lower housing member andextending about the peripheral region of the lower housing member.Internal components of the electrical switch units within the housingare not shown; and

FIG. 4B shows a magnified top perspective cross-sectional view inrendered drawing form of an aspect of the electrical switch unit in FIG.4A with the top housing member removed to reveal anelastically-resilient overmold sealing member seated in a recessdisposed along the peripheral region of the lower housing member andextending about the peripheral region of the lower housing member.Internal components of the electrical switch units within the housingare not shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described herein withreference to FIGS. 1 to 4B of the drawings. Although embodiments of thepresent invention will be described in relation to use with anelectrical switch unit, it would be appreciated that this is forillustrative purposes only and other embodiments of the inventiveconcept may be applicable in relation to other types of devices andassemblies. Further, it would be appreciated and understood that whilstthis embodiment is described for use with an electric power tool, thisis merely for purposes of illustrating functionality and alternateembodiments of the present invention may of course be used with othertypes of electrical devices such as gardening tools and home electricalappliances. Furthermore, whilst embodiments of the present inventiondescribed herein refer to electrical devices comprising an electricmotor (for instance, to drive rotation a drill bit), it would beappreciated that alternate embodiments of the present invention may alsobe applicable to electric devices which comprise a solenoid typeelectro-mechanical unit to effect operable movement (e.g. reciprocalmotion) of the electric device. As shown in FIGS. 1A and 1B theelectrical switch includes terminals (150) and connector pins (160)extending outwardly from a surface of the assembled unit.

Referring firstly to FIGS. 1A and 1B, the electrical switch unit (100)is shown comprising a first housing member (100A) and a second housingmember (100B) which is configured for attachment to the second housingmember (which will be referred as a “lower” and “upper” housing membersrespectively hereafter). The lower and upper housing members (100A,100B)may be heled in attachment together by use of any suitable attachmentmechanism such as a screw-type attachment mechanism, a friction fittingattachment mechanism or the like. In this embodiment, the lower andupper housing members (100A,100B) include respective peripheral edgeregions (100A′,100B′) that are configured for attachment together sothat the lower and upper housing members (100A,100B) may cooperativelyform an enclosed space therebetween for housing various electrical andmechanical components (140) of the electrical switch unit (100) therein.Such electrical and mechanical components (140) may for instance includea pair of electrical switching contacts of the electrical switch unit, areversing assembly (120) that is actuatable to reverse the direction inwhich the motor of the electrical device is driven, and at least aportion of a trigger actuator member (110) operably-connected with atleast one of the pair of electrical switch contacts. The triggeractuator member (110) is configured for movement relatively inwardly andoutwardly of an opening in the electrical switch unit housing(100A,100B) so as to arrange the pair of electrical switch contacts intoat least one of a closed configuration wherein power is able to besupplied from a power source of the electrical device to motor via thepair of electrical switch contacts, and, an opened configuration whereinpower is not able to be supplied from the power source to the motor ofthe electrical device via the pair of electrical switch contacts.

In this embodiment, the peripheral edge region (100A′) of the lowerhousing member (100A) includes a recess disposed along the peripheraledge region (100A′) that is configured for seating an elongateelastically-resilient polymeric sealing member (130) therein. Inalternate embodiments, the peripheral edge region (100A′) may insteadinclude a groove or a slot for seating the sealing member (130) therein.Additionally, and/or alternatively, the sealing member (130) may also bemaintained in position along the peripheral edge regions (100A′,100B′)of the lower and upper housing members (100A′,100B′) by use of anadhesive. The elongate elastically-resilient polymeric sealing member(130) is formed by extruding a material such as rubber, foam, or athermoplastic material. The approximate cross-sectional dimensions ofthe sealing member (130) may be selected based on the specificuser-requirements. The location of the sealing member (130) between thelower and upper housing members (100A,100B) not only occludes passageand ingress of particulates and water into the electrical switch unithousing but also may provide some degree of dampening of vibrations soas to alleviate damage to the electrical switch unit components (140)therein.

As can be seen in FIGS. 2A and 2B, the elongate sealing member (130)also includes a saw-tooth cross-sectional shape profile. Advantageously,when the lower and upper housing members (100A,100B) are attachedtogether, the sealing member (130) will abut against the peripheralregion of the upper housing member. The cross-sectional saw-tooth shapecontour of sealing member (130) will tend to contact with the upperhousing peripheral region in such a manner to alleviate lateral movementrelative to the upper housing member (100B).

Referring to FIGS. 3A, 4A and 4B, it can be seen that the sealingelement may be configured to complement a three-dimensional shapecontour of the peripheral region of the lower or upper housing members(100A,100B). In this case, the sealing member (130) is configured to notonly extend about the peripheral edge region of the lower and upperhousing members (100A,100B) in a first two-dimensional plane, but also,includes a portion (130A) that is configured to extend transversely fromthe two-dimensional plane in a curved contour. As can be seen such anembodiment of the present invention is suitable for accommodatingirregular or non-flat surface topologies of the housing members. In thiscase, the sealing member (130) is suitably shaped to accommodate acurved contour of a reversing module (120) of the electrical switch unit(100). In other embodiments, the flexibility and versatility of thesealing member is able to accommodate even more complexthree-dimensional shape contours of the housing member surfacetopologies. In contrast, existing approaches which for instance utiliseO-rings to effect sealing are limited in their degree of flexibility andversatility and are not suited for providing sealing along non-flat orirregular shaped surface topologies.

In certain embodiments, the sealing element (130) may be formed by firstforming the lower housing member (100A) and upper housing members (100B)from of a relatively hard plastic material. Thereafter, an overmoldingtechnique may then be used to form a relatively softelastically-resilient sealing member (130) on the peripheral edge region(100A′) of the hard plastic lower housing member (100A). The upperhousing member (100B) may thereafter be positioned for attachment withthe lower housing member (100A) with the sealing member (130) beingsandwiched between the respective peripheral edge regions (100A′,100B′)of the lower and upper housing members (100A,100B).

As can be seen in the FIG. 4B, O-rings may be used in combination withthe sealing member of this embodiments to provide additional sealingprotection. For instance, as shown in FIG. 4B, an O-ring (170) may stillbe utilised to effect sealing about the aperture of the reversing modulelever (120). Similarly, in certain embodiments, a glue or resin may beused to provide sealing in regions about the openings in the housingwhere the terminal (150) and connector pins (160) of the electricalswitch unit protrude outwardly. Such additional sealing means maycomplement the function of the sealing member (130) in preventingingress of particulates nad water into the electrical switch unithousing.

In view of the above it would be appreciated that embodiments of thepresent invention may provide various advantages over the existing art.Firstly, the novel application of a polymeric sealing member directlybetween the housing members of the electrical switch housing providessimple, low-cost and effective sealing to prevent ingress ofparticulates and water which may damage the components of the electricalswitch unit. Moreover, this reduces the relatively larger amount ofmaterials, costs and complexity which may otherwise be required toeffect sealing at the electrical switch box level rather than theelectrical switch housing level. Secondly, embodiments of the presentinvention utilise a sealing member which is better suited for effectingsealing between housing members of an electrical switch housing havingnon-flat or irregular shaped surface topologies or contours. Incontrast, currently used solutions such as O-rings are of a fixed shapeand are limited in their ability to function upon non-flat or irregularshaped surface topologies or contours. Yet further, the novelcross-sectional shape contour of the sealing member may assist inalleviating lateral movement of the sealing member to the upper housingmember in use so that sealing may be more effectively maintained.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described without departing from the scope of theinvention. All such variations and modification which become apparent topersons skilled in the art, should be considered to fall within thespirit and scope of the invention as broadly hereinbefore described. Itis to be understood that the invention includes all such variations andmodifications. The invention also includes all of the steps andfeatures, referred or indicated in the specification, individually orcollectively, and any and all combinations of any two or more of saidsteps or features.

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgment or any form of suggestion that thatprior art forms part of the common general knowledge.

What is claimed is:
 1. An electrical switch unit for use in controllingoperation of an electrical device, the electrical switch unit including:an electrical switch unit housing for housing at least a pair ofelectrical switching contacts of the electrical switch unit, saidelectrical switch unit housing including a first housing member and asecond housing member that are configured for attachment together atperipheral regions of the first and second housing members so as tocooperatively form an enclosed space for housing the pair of electricalswitching contacts therein; an actuator member operably-connected withat least one of the pair of electrical switching contacts, the actuatorbeing configured for movement relative inwardly and outwardly of anopening in the electrical switch unit housing so as to arrange the pairof electrical switching contacts into at least one of a closedconfiguration wherein power is able to be supplied from a power sourceto motor or other electrically-operable element of the electrical devicevia the pair of electrical switching contacts, and, an openedconfiguration wherein power is not able to be supplied from the powersource to the motor or other electrically-operable element of theelectrical device via the pair of electrical switching contacts; and ansealing element including an elastically-resilient polymeric material,said sealing element being configured for location between the first andsecond housing members and extending about the peripheral regions of thefirst and second housing members so as to occlude passage and ingress ofparticulates and water into the electrical switch unit housing.
 2. Anelectrical switch unit as claimed in claim 1 wherein the sealing elementis configured to complement a three-dimensional shape contour of theperipheral region of the first or second housing member.
 3. Anelectrical switch unit as claimed in claim 1 including at least one of arecess and a groove disposed along the peripheral region of at least oneof the first and second housing members configured for seating thesealing element therein.
 4. An electrical switch unit as claimed inclaim 1 wherein the sealing element includes an overmold.
 5. Anelectrical switch unit as claimed in claim 1 wherein the sealing elementincludes at least one of a rubber, a foam, and a thermoplastic material.6. An electrical switch unit as claimed in claim 1 wherein the sealingelement includes a cross-sectional shape contour includes at least onepeak and one trough region.
 7. An electrical switch unit as claimed inclaim 6 wherein the cross-sectional shape contour including a saw-toothcross-sectional shape contour.
 8. An electrical switch unit as claimedin claim 1 wherein the sealing element includes an elongate sealingelement.
 9. A method of producing an electrical switch unit for use incontrolling operation of an electrical device, the method includingsteps of: (i) providing an electrical switch unit housing for housing atleast a pair of electrical switching contacts of the electrical switchunit, said electrical switch unit housing including a first housingmember and a second housing member that are configured for attachmenttogether at peripheral regions of the first and second housing membersso as to cooperatively form an enclosed space for housing the pair ofelectrical switching contacts therein; (ii) providing an actuator memberoperably-connected with at least one of the pair of electrical switchingcontacts, the actuator being configured for movement relative inwardlyand outwardly of an opening in the electrical switch unit housing so asto arrange the pair of electrical switching contacts into at least oneof a closed configuration wherein power is able to be supplied from apower source to motor or other electrically-operable element of theelectrical device via the pair of electrical switching contacts, and, anopened configuration wherein power is not able to be supplied from thepower source to the motor or other electrically-operable element of theelectrical device via the pair of electrical switching contacts; and(iii) providing a sealing element including an elastically-resilientpolymeric material, said sealing element being configured for locationbetween the first and second housing members and extending about theperipheral regions of the first and second housing members so as toocclude passage and ingress of particulates and water into theelectrical switch unit housing.
 10. A method as claimed in claim 9including a step of forming the sealing element to complement athree-dimensional shape contour of the peripheral region of the first orsecond housing member.
 11. A method as claimed in claim 9 including atstep of forming at least one of a recess and a groove disposed along theperipheral region of at least one of the first and second housingmembers configured for seating the sealing element therein.
 12. A methodas claimed in claim 9 wherein the sealing element includes an overmold.13. A method as claimed in claim 9 including a step of forming thesealing element from at least one of a rubber, a foam, and athermoplastic material.
 14. A method das claimed in claim 9 including astep of forming the sealing element wherein a cross-sectional shapecontour of the sealing element includes at least one peak and one troughregion.
 15. A method das claimed in claim 14 wherein the cross-sectionalshape contour includes a saw-tooth cross-sectional shape contour.
 16. Amethod as claimed in claim 9 wherein the sealing element is formed as anelongate sealing element.